private void DiscardNotReachable(Partition blocks, List <Transition> transitions, Func <Transition, int> getFrom, Func <Transition, int> getTo)
{
var adjacentTransitions = new AdjacentTransitions(StateCount, transitions, getFrom);
foreach (var state in blocks.MarkedInSet(0))
{
foreach (var transition in adjacentTransitions[state])
{
blocks.Mark(getTo(transitions[transition]));
}
}
blocks.DiscardUnmarked();
transitions.RemoveAll(transition => blocks.SetOf(getFrom(transition)) == -1);
}
public DFA Minimize()
{
// We will be modifying this list of transitions and we don't want to mess up our own
var transitions = new List <Transition>(this.transitions);
var blocks = new Partition(StateCount);
// Reachable from start
blocks.Mark(StartState);
DiscardNotReachable(blocks, transitions, t => t.From, t => t.To);
// Reachable from final
foreach (var finalState in finalStates)
{
blocks.Mark(finalState);
}
DiscardNotReachable(blocks, transitions, t => t.To, t => t.From);
// Split final states from non-final
foreach (var finalState in finalStates)
{
blocks.Mark(finalState);
}
blocks.SplitSets();
// Cords partition to manage transitions
var cords = new Partition(transitions.Count);
// Split transitions by input
cords.PartitionBy(transition => transitions[transition].OnInput);
//Split blocks and cords
var adjacentTransitions = new AdjacentTransitions(StateCount, transitions, t => t.To);
var blockSet = 1;
for (var cordSet = 0; cordSet < cords.SetCount; cordSet++)
{
foreach (var transition in cords.Set(cordSet))
{
blocks.Mark(transitions[transition].From);
}
blocks.SplitSets();
for (; blockSet < blocks.SetCount; blockSet++)
{
foreach (var state in blocks.Set(blockSet))
{
foreach (var transition in adjacentTransitions[state])
{
cords.Mark(transition);
}
}
cords.SplitSets();
}
}
// Generate minimized DFA
var minDFA = new DFA(blocks.SetCount, blocks.SetOf(StartState));
// Set Final States
foreach (var finalState in finalStates)
{
var set = blocks.SetOf(finalState);
if (set != -1) // not all final states may have been reachable
{
minDFA.AddFinalState(set);
}
}
// Create transitions
for (var set = 0; set < cords.SetCount; set++)
{
var transition = transitions[cords.SomeElementOf(set)];
var @from = blocks.SetOf(transition.From);
var to = blocks.SetOf(transition.To);
minDFA.AddTransition(@from, transition.OnInput, to);
}
return(minDFA);
}
